Supporting wooden panel element for constructing ceilings or bridges and use of a screw for connecting boards to form a panel element

ABSTRACT

In a wooden panel element ( 1 ) for ceiling structures or for bridge construction there is provided a plurality of boards ( 25 ) standing on edge perpendicular to the plane of the panel element ( 1 ) and running along the entire length thereof, which boards are joined together by screw fastenings. The individual boards ( 25 ) are joined together at least partly by screws ( 27 ) driven at an acute angle to the surface thereof, each of these screws ( 27 ) passing through two successive boards ( 25 ). Also provided close to the upper edge ( 30 ) and the lower edge ( 31 ) of the boards ( 25 ) are screws ( 28 ) driven at right angles to the surface ( 26 ) of the boards ( 25 ).

The invention relates to a load-bearing wooden panel element for ceilingstructures or for bridge construction, comprising a plurality ofindividual layers of boards standing on edge perpendicular to the planeof the panel element and preferably running along the entire lengththereof, which boards are joined together by screw fastenings, and itfurther relates to the use of a screw for joining boards as a panelelement.

The oldest and most familiar way of fastening board stacks is bynailing. In nailing, the forces between the boards are transferred byshearing in the nails and by hole-widening pressure between nail andwood. This kind of joint is relatively compliant and therefore of onlylimited effectiveness. Heretofore, prior art applications of screwedboard stacks have depended on a principle of action analogous tonailing, or in other words shearing and hole-widening pressure.

There have already been published load-bearing panel elements (U.S. Pat.No. 1,944,237) in which a plurality of boards standing on edge arejoined together by tie rods passing through all boards. In addition, theindividual boards are joined together by nailing so that they aretemporarily held mutually together during construction of such a stack.In the so-called transversely prestressed board stacks, the forcesbetween the individual boards are transferred by friction, whichpresupposes a steady contact pressure. The transverse prestresstherefore must always be guaranteed up to a certain level. Since woodhas a tendency to shrinkage and creep deformations, it must beconstantly ensured that the tension rods can be retightened.

In such a load-bearing wooden panel element, it is essential that theindividual layers of boards be mutually firmly braced or be mutuallyfirmly pressed, in order that they can better absorb the load. It mustbe realized in this known embodiment that only a certain number ofboards standing on edge can be joined together as a panel element bytension rods. Thus it is not possible to make arbitrary widths of suchpanel elements, for example for use in ceiling structures or in bridgeconstruction, and so individual panel elements, which are no longerjoined together, are then disposed next to each other.

There have also been published other design variants for nailed,beam-like wooden structural members (DE C 842709) and for board-stackelements (DE A 19513729), in which individual boards are joined togetheras one element by nailed and/or screwed joints.

The object of the present invention is now to provide a load-bearingwooden panel element of the type mentioned in the introduction, whichcan be made with arbitrary length and width, wherein the forcesoccurring on individual layers of boards during loading of this panelelement can be transferred to the greatest possible width of the panelelement

According to the invention, it is proposed for this purpose that theindividual boards be joined together at least partly by screws driven atan acute angle to the surface thereof and disposed at leastapproximately in a plane running transverse to the longitudinal extentof the panel element, which screws pass through at least two successiveboards.

By these features according to the invention, the situation is achievedthat the occurring forces are transferred to a plurality of layers ofboards disposed next to each other, even in the case of point-like orsmall-area loading of such a panel element, since the successive layersof boards are joined together in, so to speak, hook-like manner by thescrews driven at an acute angle. Moreover, it is achieved by the use ofscrews that the successive layers of boards are effectively held andbraced mutually. Thus, even in the case of possible shrinkage orexpansion of the natural wood product, no change of the mutual fasteningof the boards is necessary, since these always remain intimately andintensively joined to each other. By virtue of the special arrangementof the screws, these should be stressed primarily in longitudinaldirection, or in other words by tension or compression, thus ensuringgreat effectiveness with respect to load-bearing capacity and stiffness.

It is further proposed that, in successive boards or in every secondboard, screws with crosswise directions be driven into successive planesseparated by a spacing and disposed perpendicular to the boards. Thisfeature offers the guarantee that in precisely these fastening zones,each layer of board is for practical purposes attached on both sides tothe neighboring board by a hook-like arrangement, so that it cantransfer large forces to a large area of a panel element.

In order to create even more fastenings between the individual boards inaddition to this special mutual fastening for extensive transmission offorces, it is proposed that, in addition to the screws driven at anacute angle to the surface of the boards, further screws be used whichare driven at right angles to the surface of the boards, each of whichscrews passes through at least three successive boards. By theseadditionally driven-in screws it is achieved that joining of thesuccessive layers of boards takes place almost in the manner of a truss,specifically since the screws driven at an acute angle and at rightangles complement each other.

In this connection it is advantageous for the screws driven at rightangles to the surface of the boards to be driven alternately into everysecond board and to pass through three layers of boards. This createsthe possibility of a repeatedly overlapping fastening between theindividual boards since, for example, the screws driven at an acuteangle pass through two boards and the screws driven at right angles eachpass through three layers of boards. In this way optimal force transferto large areas of the wooden panel element can be achieved.

In one advantageous embodiment is it provided that screws driven inpairs at an acute angle and at fight angles to the surface of the boardsare disposed successively at a predetermined grid pitch and in twoplanes separated by a small spacing. Thereby pairs of successivefastener planes separated by a small spacing are then practically alwayscreated at specified spacings, in order in this way to achieve theoptimum in mutual joining of the boards and in the capability of mutualforce transfer.

In this connection, it is advantageous for the screws in one of theplanes disposed at the grid pitch always to be driven to be inclined atan acute angle in one direction and those in the other plane to beinclined at an acute angle in the opposing direction, the two screws ineach pair being driven crosswise relative to each other at therespective surfaces of boards fitting the grid pitch, but being disposedin successive planes separated by a small spacing. During constructionof the panel element, therefore, two screws are practically alwaysdriven at an acute angle into planes disposed next to each other butseparated by a small spacing, one directed obliquely from top to bottomand the other obliquely from bottom to top. In this case two fasteningplanes are always present next to each other in the manner of trusses,so to speak, thus ensuring optimal mutual joining of the individualboards as a panel element and optimal transfer of forces.

In this connection, it is advantageous precisely in the sense of formingtruss-like fastening planes for screws inclined at an acute angle in theone direction to be provided in a plane fitting the corresponding gridpitch relative to the length of the panel element and, furthermore, forscrews driven at right angles to the surface of the boards to beprovided close to the top and bottom board edge. In this way, top andbottom tension or compression elements are formed practically transverseto the longitudinal extent of a panel element, and load-bearing elementsare produced by screws inclined at an acute angle therebetween. Sincethe two screws driven at an acute angle are additionally disposedcrosswise, two load-bearing zones interacting with each other arecreated in the immediately successive planes fitting to the grid pitch.

It is advantageous, and is also favorable from the assembly viewpoint,for the screws driven to be inclined at an acute angle to the surface ofthe boards to include an angle of approximately 45° with the surface, sothat the screws disposed crosswise relative to each other in the closelysuccessive planes form right angles with each other. Thereby the optimumcapability for mutual force transfer between the successive boards canbe achieved.

An advantageous embodiment provides that screws oriented at right anglesto the surface of the board are driven into every second of thesuccessive boards, each screw driven successively into every secondboard at right angles to the surface being paired with the other screwof the plane disposed therebeside at a small spacing therefrom. Thisoffers the possibility that the screws driven at right angles to thesurface overlap each other by a corresponding extent in the immediatelyadjacent planes without providing a continuous fastening. The screwsdriven at right angles to the surface form a kind of clamping element ofknown type passing through the entire width of the panel element, exceptthat in this case there are used only short screws, disposed in paralleland overlapping each other alternately at their ends. In this way,however, they are distributed continuously over the entire width of theload-bearing panel element.

A particularly advantageous embodiment is achieved when the screwsdriven at an acute angle to the surface of the boards and the screwsdriven at right angles to the surface of the boards have the samelength, in which case the screws driven at an acute angle each passthrough two neighboring boards and the screws driven at right angles tothe surface of the boards each pass through three successive boards. Bythis feature there is needed only one design of a screw, which can beused both for driving in at an acute angle and for driving in at rightangles to the surface. Since only a single fastening element isnecessary, assembly of the panel element therewith is made substantiallyeasier.

An embodiment which is advantageous in particular for assembly of thepanel element provides that fixing screws for temporary mutual fixationof successive boards are driven mid-way relative to the grid pitch andalso relative to the height of the panel element. The fixing screwsprovided in this case hold the successive boards until the screws drivenat an acute angle and at right angles to the surface have been placed.These fixing screws, provided as an assembly aid, remain in theload-bearing panel element but do not influence the load-bearingcapability of the panel element.

The screw used according to the invention is characterized in that athreaded portion is provided on a shank at least at the two end regionsthereof, in which case the two threaded portions are matched to eachother in their course, or one continuous threaded portion is providedover the entire length, or else two successive portions of differentdiameters but having the same thread pitch are provided.

To obtain a load-bearing wooden panel element with appropriateload-bearing capability, it is necessary to use a corresponding screw,in which connection corresponding forces can be transferred precisely bya relatively long thread engagement. The manufacturing capabilities forlong threads are limited to a certain size for the most part. However,options exist for providing two threaded portions. By means of thedesign comprising one continuous thread, the inherently simplestembodiment is created, in which case, however, an appropriate structuralgeometry must be provided for the drive of a driving tool. In preciselysuch a situation, however, it is then necessary under certaincircumstances to have a certain diameter available, in order to be ableto transmit the necessary torque with the driving tool. Anotherpossibility, however, is to provide the drive for a driving tool in ashank portion of larger diameter. If the thread of the portion with thelarger diameter is to engage in the already existing thread with thesmaller diameter, however, then the two threaded portions must bematched to each other.

One possibility of how an exactly continued thread flight on a largerportion with the same thread pitch can be avoided in the small and inthe large portion exists when the portion with the larger diameter has acore diameter corresponding at least approximately to the outside threaddiameter of the portion with the smaller diameter. Then the same threadpitch is indeed present both in the portion with the larger diameter andin the portion with the smaller diameter, without it being necessarythat the thread on the portion with the larger diameter begin exactly bya multiple of the thread pitch of the thread with the smaller diameter.In such an embodiment, the thread that has been formed by the portionwith smaller diameter is practically already destroyed by the corediameter of the portion with the larger diameter and a new thread isformed in the board.

Precisely for the screws used according to the invention is it usefulfor a recessed drive to be provided for a driving tool at the free endof the portion with larger diameter. Thereby the possibility exists ofusing practically a headless screw, so that it is not necessary tocountersink the screws. Thus the screws can always be drivensufficiently far that they are positioned under the surface of thecorresponding board, so that the next board can again be placed flushfor further assembly.

Further features and particular advantages according to the inventionwill be explained in more detail in the following description withreference to the drawings, wherein:

FIG. 1 shows a section through a partial structure of a bridge builtwith the panel element according to the invention;

FIG. 2 shows an oblique view of a partial section of a panel element;

FIG. 3 shows a section through the entire structure of a bridgeconstructed with the panel element according to the invention;

FIG. 4 shows a vertical section through the panel element along lineIV—IV in FIG. 2 with schematically illustrated arrangement of theinserted screws;

FIG. 5 shows a view of the surface of a board in use with schematicallyillustrated arrangement of the inserted screws;

FIG. 6 shows a top view of a section of a panel element, wherein thescrews driven at a right angles the surface of the boards areschematically illustrated;

FIG. 7 shows a similar top view of a section of the panel element,wherein the screws driven at an acute angle are schematicallyillustrated;

FIG. 8 shows a vertical section through a partial region of the panelelement in which an inserted crew is driven at right angles to thesurface of a board;

FIG. 9 shows a vertical section through a panel element in the region ofscrews driven at an acute angle to the surface of the boards.

FIG. 1 and 3 illustrate one possible structure of a wooden bridge. Thebridge slab is formed from a load-bearing wooden panel element 1, thedesign and structure of which will be further explained hereinafter. Onpanel element 1 there is applied a moisture insulation 2, over which thebridge liner 3 is, then laid. The curb 4 is also made of wood. To thiscurb 4 and to the side edges of panel element 1 there are fastenedrailing posts 5 by bolts 6 and 7. To railing posts 5 there is attachedand fastened by screws 9 a handrail 8, which can also be made of wood.The handrail 8 can additionally be provided with a copper covering 10.FIG. 3 illustrates a section through such a bridge in its longitudinalextent. Wooden ground beams 13 are seated on corresponding foundationparts 11, 12. Bearing beams 16 are braced by appropriate uprights 14 andstruts 15. The actual beams 18 forming the bracing can be verticallyadjusted by wedges 17. Panel element 1 then rests on beam 18. Thecontinuing road is attached to appropriate connecting beams 19. Planks20 standing on edge are provided to form a boundary to the solidmaterial, while an appropriate boundary between the fastened part andthe creek bed to be bridged is provided by an appropriate backing 21,excavation 22 and a cut-off sill placed on a foundation 23.

The load-bearing panel element 1 according to the present invention canbe used not only for bridge construction but also for ceiling structuresand naturally also for construction of walls or similar structures ifnecessary. Each panel element comprises a plurality of individual layersof boards 25 standing on edge perpendicular to the plane of the panelelement 1 and preferably running along the entire length thereof.Maximum strengths are achieved when the boards are each madecontinuously over the entire length of the panel element For certainapplications—especially for longer elements—it would also be possible,however, to provide, in addition to or instead of continuous boards,boards which are partly or completely continuous only over part of thelength of the panel element, and which are then joined appropriatelytogether. For example, it would also be possible to provide a pluralityof shorter elements, which nevertheless overlap repeatedly in theindividual layers. Within the scope of the invention it is entirelypossible to use adhesives such as glue in addition to the screwfastenings. By virtue of the features according to the invention,however, this is not necessary for mutual joining of boards 25 as apanel element.

The features according to the invention now lie in the special fasteningof the individual boards 25 to form the load-bearing wooden panelelement. The individual boards 25 are joined together by screws 27driven at an acute angle to the surface 26 thereof, these screws drivenat an acute angle being positioned at least approximately in a planerunning transverse to the longitudinal extent of panel element 1. In theinserted position, screws 27 are therefore driven to run obliquely fromtop to bottom or from bottom to top. As can be seen from the schematicdiagram in FIG. 4, screws 27 pass through at least two successive boards25. In successive boards 25 or if necessary only in every second board25, screws with crosswise directions are driven into successive planes29 and 39 separated by a spacing and disposed transverse to boards 25.

In addition to the screws 27 driven at an acute angle to the surface 26of the boards 25, there are provided further screws 28 which each passthrough at least three successive boards 25 and are inserted at rightangles to the surface 26. In this connection, the screws 28 are sodisposed, as can be seen in particular from FIG. 4 and 6, that they aredriven alternately into every second board 25 and pass through threelayers each of boards 25. Pairs of screws 27 and 28 driven respectivelyat an acute angle and at right angles to the surface 26 of the boards 25are provided successively at a predetermined grid pitch R and in twoplanes 29, 39 separated from each other by a small spacing A.

As regards FIG. 7, it can be stated that the orientations shown thereinof the screws 27 driven at an acute angle are chosen merely for carity.Viewed from above, the screws 27 would lie practically in one plane inone direction, and therefore would be disposed one above the other inthis view, thus making a clear understanding impossible. The specialmethod of illustration in FIG. 7 was chosen in order to make it clearthat, in this embodiment, the screws 27 driven at an acute angle to thesurface 26 pass through two boards and are inserted practically startingfrom the surface of each board.

The screws 27 disposed in one of the two planes 29, 39 are always drivento be inclined at an acute angle in one direction, and the screwsdisposed in the other plane 29, 39 are inclined at an acute angle in theopposing direction. Thus pairs of screws 27 disposed crosswise areprovided at each surface 26 of boards 25 fitting the grid pitch R, butthey occupy successive planes 29 and 39 separated from each other withsmall spacing A.

In each plane 29 or 39 there are provided, at the corresponding gridsize R relative to the length of panel element 1, screws 27 inclined atan acute angle in one direction and, furthermore, screws 28 driven atright angles to the surface 26 of the boards 25, close to the upperboard edge 30 and to the lower board edge 31. A truss-like arrangementof screws 27 and 28, each with spacing A, is practically created, and sooptimal mutual fastening and load distribution is possible. As shown inparticular by FIG. 4 and 9, the screws 27 driven to be inclined at anacute angle to the surface 26 of boards 25 include an angle a ofapproximately 45° with the surface 26, and so the screws 27 disposedcrosswise relative to each other in the closely spaced successive planes29, 39 are oriented at right angles to each other.

As specially illustrated in FIG. 6, and also in FIG. 4, screws 28oriented at right angles to the surface 26 are driven into every secondone of the successive boards 25, each screw 28 driven into every secondboard 25 paired with the other screw of the plane 29 or 39 disposedtherebeside at a small spacing A therefrom. The screws 28 thereforeoverlap repeatedly at their end regions, although this overlap isseparated by the spacing A of the two planes 29, 39.

It is particularly advantageous for the screws 27 driven at an acuteangle and the screws 28 driven at right angles to have the same length.The screws driven at an acute angle then pass through two neighboringboards 25 and the screws driven at right angles each pass through threesuccessive boards 25. The unique advantage, however, lies in the factthat the same screws can always be used for the application of screws 27and the application of screws 28. In all cases, therefore, only one kindof screw is necessary for assembly of such a panel element, and the samedesign and length will be chosen if possible for the screws additionallyrequired for constructing a bridge.

The grid pitch R is adapted according to the unsupported bearing lengthof the panel element, and the spacing A of the two planes 29 and 39 canalso be adjusted to the various circumstances. Criteria for specialadaptation can include, for example, the span of such a panel element,the particular load-bearing capacity of the panel element, the type ofwood used, and also the type of screws used.

FIG. 5 shows that fixing screws 32 for temporary mutual fixation ofsuccessive boards 25 are driven mid-way relative to the grid spacing Rand also relative to the height H of panel element 1. The fixing screws32 constitute a kind of assembly aid in constructing the panel element,in that the next board can be firmly joined to the preceding board or tothe already completed section of the panel element at certain spacings,thus making it easier to drive screws 27 and 28. Naturally the fixingscrews do not always have to be disposed mid-way relative to a gridpitch and mid-way relative to the height H. Thereby it is merely ensuredthat the fixing screws 32 are not disposed in the region of or close tothe planes 29 and 39.

The diagrams of FIG. 8 and 9 show a special embodiment of screws 27 and28. On a shank 33 there are provided two portions 34 and 35 of differentdiameter, each with a threaded portion 36, 37. The two threaded portionshave the same thread pitch. Thereby mutual displacements of thesuccessive boards 25 do not occur during the driving process. Moreover,it is ensured that the thread already cut by threaded portion 36 cannotbe destroyed by threaded portion 37. In this connection, it is usefulfor the portion 35 with the larger diameter to have a core diametercorresponding at least approximately to the outside thread diameter ofportion 34. Thereby it is also possible for the threaded portions 36 and37 to have the same thread pitch, even though an exactly continuousthread does not have to be present over the entire length of the screw.

If instead of portions 34, 35 with different diameter there were presenttwo threaded portions at least in the end regions, these threadedportions would have to be matched exactly to each other, so that thetrailing threaded portion could begin to engage exactly in the threadalready cut by the first threaded portion. For a shank 33 withcontinuously constant diameter and continuous thread, it is inherentlyclear that the same pitch is present throughout. It would also beinherently conceivable, however, for the two threaded portions 36 and 37to have slightly different thread pitch, in which case the threadedportion 37, for example, could have a slightly smaller thread pitch. Insuch an embodiment, an additional effect could be achieved in that thetwo successive boards are correspondingly drawn toward each other andthus pressed against each other to achieve prestressed condition.

At the free end of the portion 35 with larger diameter there is formed arecessed drive 38 for a driving tool. Such a screw 27 or 28 thereforedoes not have a head projecting beyond the thread, and so no particularforces are needed to countersink the screw at the surface of therespective board. If the screws are to be countersunk only slightly, itis also possible to use screws with larger heads, thus permitting betterleverage by the driving tool. Such screws can be provided with, forexample, a countersunk head.

Within the scope of the invention, it would also be possiblesuccessively to dispose more than two portions 34, 35 of different shankdiameter, if this would contribute to even better joining and mutualbracing of the successive boards 25.

It would also be conceivable to provide only one plane 29 or 39 ofscrews 27, 28 at the grid pitch R, in which case the screws 27 driven atan acute angle are inclined in opposing directions at every second gridpitch R.

The special advantages of the present invention lie in the fact that theassembly of a panel element can be achieved in simple manner on thespot, and that the successive boards of the panel element are alwaysoptimally braced against each other and thus can always be used for thebest possible load distribution without the need for retightening ofscrewed joints.

What is claimed is:
 1. A load-bearing wooden panel element for ceilingstructures or for bridge construction, comprising a plurality ofindividual layers of boards standing on edge perpendicular to the planeof the panel element, which boards are joined together by screwfastenings, characterized in that the individual boards (25) are joinedtogether at least partly by screws (27) driven at an acute angle to thesurface thereof and disposed at least approximately in a plane runningtransverse to the longitudinal extent of the panel element (1), whichscrews pass through at least two successive boards (25).
 2. A panelelement according to claim 1, characterized in that, in successiveboards (25) or in every second board (25), screws (27) with crosswisedirections are driven into successive planes (29, 39) separated by aspacing (A) and disposed perpendicular to the boards (25).
 3. A panelelement according to claim 1, characterized in that, in addition to thescrews (27) driven at an acute angle to the surface (26) of the boards(25), further screws (28) are used which are driven at right angles tothe surface (26) of the boards (25), each of which screws passes throughat least three successive boards (25).
 4. A panel element according toclaim 3, characterized in that the screws (28) driven at right angles tothe surface (26) of the boards (25) are driven alternately into everysecond board (25) and each passes through three layers of boards (25).5. A panel element according to claim 1, characterized in that screws(27, 28) driven in pairs at an acute angle and at right angles to thesurface (26) of the boards (25) are disposed successively at apredetermined grid pitch (R) and in two planes (29, 39) separated by asmall spacing (A).
 6. A panel element according to claim 5,characterized in that the screws (27) in one of the planes (29, 39)disposed at the grid pitch (R) are always driven to be inclined at anacute angle in one direction and those in the other plane (29, 39) areinclined at an acute angle in the opposing direction, the two screws(28) in each pair being driven crosswise relative to each other at therespective surfaces (26) of boards (25) fitting the grid pitch (R), butbeing disposed in successive planes (29, 39) separated by a smallspacing (A).
 7. A panel element according to claim 6, characterized inthat screws (27) inclined at an acute angle in the one direction areprovided in a plane (29, 39) fitting the corresponding grid pitch (R)relative to the length of the panel element (1) and, furthermore, screws(28) driven at right angles to the surface (26) of the boards (25) areprovided close to the top and bottom board edge (30, 31).
 8. A panelelement according to claim 1, characterized in that the screws (28)driven to be inclined at an acute angle to the surface (26) of theboards (25) include an angle (a) of approximately 45° with the surface(26), so that the screws (27) disposed crosswise relative to each otherin the closely successive planes (29, 39) form right angles with eachother.
 9. A panel element according to claim 1, characterized in thatscrews (28) oriented at right angles to the surface (26) of the board(25) are driven into every second of the successive boards (25), eachscrew (28) driven successively into every second board (25) at rightangles to the surface (26) being paired with the other screw of theplane (29, 39) disposed therebeside at a small spacing (A) therefrom.10. A panel element according to claim 1, characterized in that thescrews (27) driven at an acute angle to the surface (26) of the boards(25) and the screws (28) driven at right angles to the surface (26) ofthe boards (25) have the same length, in which case the screws (27)driven at an acute angle each pass through two neighboring boards (25)and the screws (28) driven at right angles to the surface (26) of theboards (25) each pass through three successive boards (25).
 11. A panelelement according to claim 1 or one of the preceding claims,characterized in that fixing screws (32) for temporary mutual fixationof successive boards (25) are driven mid-way relative to the grid pitch(R) and also relative to the height (H) of the panel element (1).
 12. Ascrew for joining boards as a panel element according to claim 1, inwhich a threaded portion (36, 37) is provided on a shank (33) at leastat the two end regions thereof, in which case the two threaded portions(36, 37) are matched to each other in their course, or one continuousthreaded portion is provided over the entire length, or else twosuccessive portions (34, 35) of different diameters but having the samethread pitch are provided.
 13. A screw according to claim 12, in whichthe portion (35) with the larger diameter has a core diametercorresponding at least approximately to the outside thread diameter ofthe portion (34) which has the smaller diameter.
 14. A screw accordingto claim 12, in which a recessed drive (38) is provided for a drivingtool at the free end of the portion (35) with larger diameter.